(1) Field of the Invention
The present invention relates to a semiconductor-containing glass having a high nonlinear optical effect which can be used in the fields of optical information, for example, as optical switch and optical wavelength transformation element, and a method for producing same.
(2) Description of Prior Art
As materials having a high nonlinear optical effect, there are used those which are formed by alternately laminating semiconductors such as GaAs and AlGaAs of several ten .ANG. in thickness. In a thin film material comprising laminated semiconductors, a quantum size effect by which electrons and holes are configured in layers is exhibited by making the thickness of each layer to less than several ten .ANG. and thus a high nonlinear susceptibility is obtained. Since such thin film material has the structure comprising a substrate on which semiconductors are laminated, electrons and holes are merely confined in one dimensional direction of laminate. If semiconductor can be confined three-dimensionally in a matrix, it is expected that higher nonlinear susceptibility can be obtained.
As materials in which semiconductor is three-dimensionally confined, those which are produced by incorporating semiconductor microcrystal in a multi-component glass, have been noticed recently. A representative example of such glass is one which contains less than about 1% of CdS.sub.x Se.sub.(1-x) micro-crystal and this is commercially available as filter glass. Such glass is produced by mixing CdS and Se with glass raw materials such as silica sand, soda ash, alumina, zinc oxide, etc., melting the mixture with heat to prepare a glass in which Cd.sup.2+, S.sup.2- and Se.sup.2- are uniformly dispersed in the form of ion, and reheating this glass at 600.degree.-700.degree. C. to precipitate CdS.sub.x Se.sub.(1-x) crystal.
A glass containing CuCl crystal is also produced in addition to the glass containing CdS.sub.x Se.sub.(1-x) crystal. In this case, preparation of glass by melting raw materials and precipitation of CuCl crystal by reheating treatment are the same as those for production of the glass containing CdS.sub.x Se.sub.(1-x) crystal.
When a glass containing semiconductor crystal is produced by the above method, firstly a uniform glass must be prepared by melting glass raw materials. However, since solubility of CdS and Se in glass melt is low, a glass containing a large amount of CdS and Se cannot be produced. Furthermore, S and Se readily volatilize at high temperature and selective volatilization of these elements occur during production of glass. Therefore, contents of S and Se in the glass decrease. Besides, control of the contents is not easy. For these reasons, content of CdS.sub.x Se.sub.(1-x) crystal is merely less than 1% and as a result, the glass is low in nonlinear susceptibility and is not effective as nonlinear optical material.
Furthermore, in order to inhibit volatilization of S and Se, melting temperature of glass must be lowered and thus, composition of glass is limited to multi-component glass in which content of SiO.sub.2 is reduced to 70% or less. Therefore, the resulting glass is low in strength and durability as glass material and lacks reliability.